The disclosure relates generally to gas turbines, and more specifically, to a pneumatically-actuated air flow modulator for a fuel nozzle in a gas turbine.
Gas turbines typically include a compressor, a combustor section including one or more combustors, and at least one turbine section. Compressor discharge air is channeled into each combustor where fuel is injected via a plurality of fuel nozzles, mixed with air, and burned. The combustion gases are then channeled to the turbine section which extracts energy from the combustion gases.
Gas turbine combustion systems typically operate over a wide range of flow, pressure, temperature, and fuel/air ratio operating conditions. Controlling combustor performance is required to achieve and maintain satisfactory overall gas turbine system operation and to maintain acceptable emissions levels (e.g., NO and CO levels).
With conventional combustion systems, it is very difficult to meet emissions limits when even one fuel nozzle of a combustor is turned off. This is because the air that continues to flow through that fuel nozzle quenches the reactions of fuel and air in the flames from the remaining operating fuel nozzles, thereby preventing complete burnout of CO.